Kentrosaurus: Difference between revisions

'''''Kentrosaurus''''' ({{IPAc-en|ˌ|k|ɛ|n|t|r|oʊ|ˈ|s|ɔːr|ə|s}} {{respell|KEN|troh|SOR|əs}}; {{lit|prickle lizard}}) is a [[genus]] of [[stegosaurid]] [[dinosaur]] from the [[Late Jurassic]] in [[Lindi Region]] of [[Tanzania]]. The [[type species]] is '''''K. aethiopicus''''', named and described by [[German people|German]] [[Palaeontology|palaeontologist]] [[Edwin Hennig]] in 1915. Often thought to be a "[[Primitive (phylogenetics)|primitive]]" member of the [[Stegosauria]], several recent [[cladistic]] analyses find it as more derived than many other stegosaurs, and a close relative of ''[[Stegosaurus]]'' from the [[North American]] [[Morrison Formation]] within the [[Stegosauridae]].

The first fossils of ''Kentrosaurus'' were discovered by the [[Germay|German]] Tendaguru Expedition in 1909, recognised as belonging to a [[Stegosauria|stegosaur]] by expedition leader [[Werner Janensch]] on 24 July 1910, and described by [[German people|German]] [[Palaeontology|palaeontologist]] [[Edwin Hennig]] in 1915.<ref name=Hennig1915/> The name ''Kentrosaurus'' was coined by Hennig and comes from the [[Ancient Greek|Greek]] ''{{lang|grc-Latn|kentron}}''/{{lang|grc|κέντρον}}, meaning "sharp point" or "prickle", and ''{{lang|grc-Latn|sauros}}''/{{lang|grc|σαῦρος}} meaning "lizard",<ref name=Liddell1980/> Hennig added the [[specific name (zoology)|specific name]] ''aethiopicus'' to denote the provenance from Africa.<ref name=Hennig1915/> Soon after its description, a controversy arose over the stegosaur's name, which is very similar to the [[ceratopsian]] ''[[Centrosaurus]]''. Under the rules of biological nomenclature, forbidding [[Homonym (biology)|homonymy]], two animals may not be given the same name. Hennig renamed his stegosaur ''Kentrurosaurus'', "pointed-tail lizard", in 1916,<ref name="Hennig1916a" /> while Hungarian paleontologist [[Franz Nopcsa von Felső-Szilvás|Franz Nopcsa]] renamed the genus ''Doryphorosaurus'', "lance-bearing lizard", the same year.<ref name="Nopcsa16" /><ref name="Nopcsa16b" /> If a renaming had been necessary, Hennig's would have had priority.<ref name="Hennig1916b" /> However, because the spelling is different, both ''Doryphorosaurus'' and ''Kentrurosaurus'' are unneeded replacement names; ''Kentrosaurus'' remains the valid name for the genus with ''Kentrurosaurus'' and ''Doryphorosaurus'' being its [[Juniorjunior objective synonym|junior objective synonyms]]s.<ref name="dinosauria04" />[[File:Kentrosaurus brain and ganglium.JPG|thumb|[[Endocasts]] of the sacral [[ganglion]] and brain at Museum of Paleontology of Tübingen.]]

Although no complete individuals were found, some material was discovered in association, including a nearly complete tail, hip, several dorsal vertebrae and some limb elements of one individual. These form the core of a mount in the [[Museum für Naturkunde]] by [[Werner Janensch|Janensch]].<ref name=Janensch1925/> The mount was dismantled during the museum renovation in 2006/2007, and re-mounted in an improved pose by [http://www.rescast.com/ Research Casting International].<ref name=MallROM/> Some other material, including a braincase and spine, was thought to have been misplaced or destroyed during [[World War II]].<ref name=Glut97/> However, all the supposedly lost cranial material was later found in a drawer of a basement cupboard.<ref name=Galton88/>

From 1909 onwards, ''Kentrosaurus'' remains were uncovered in four quarries in the ''Mittlere Saurierschichten'' (Middle Saurian Beds) and one quarry in the ''Obere Saurierschichten'' (Upper Saurian Beds).<ref name=MallisonRealLecto/> During four field seasons, the German Expedition found over 1200 bones of ''Kentrosaurus'', belonging to about fifty individuals,<ref name=Hennig1925/> many of which were destroyed during the Second World War.<ref name=Maier2003/> Today, almost all remaining material is housed in the [[Museum für Naturkunde]] Berlin (roughly 350 remaining specimens), while the museum of the Institute for Geosciences of the [[University of Tübingen]] houses a composite mount, roughly 50% of it being original bones.<ref name=MallisonRealLecto/>

In the original description, Hennig did not designate a [[holotype]] specimen. However, in a detailed monography on the osteology, systematic position and palaeobiology of ''Kentrosaurus'' in 1925, Hennig picked the most complete partial skeleton, today inventorised as '''MB.R.4800.1 through MB.R.4800.37''', as a lectotype (see [[syntype]]).<ref name="Hennig19252:3" /><ref name=":4" /> This material includes a nearly complete series of tail vertebrae, several vertebrae of the back, a [[sacrum]] with five sacral vertebrae and both [[Ilium (bone)|ilia]], both [[Femur|femora]] and an [[ulna]], and is included in the mounted skeleton at the [[Museum für Naturkunde]] in [[Berlin]], [[Germany]]. The type locality is Kindope, [[Tanzania]], north of Tendaguru hill.<ref name="Hennig19252:4">Janensch, W. (1925). Ein aufgestelltes skelett des stegosauriers Kentrurosaurus aethiopicus E. Hennig aus den Tendaguru-schichten Deutsch-Ostafrikas. ''Palaeontographica-Supplementbände'', 255-276.</ref>

Unaware that Hennig had already defined a lectotype, [[Peter Galton]]<ref name="Galton1982" /> selected two dorsal vertebrae, specimens MB.R.1930 and MB.R.1931, from the material figured in Hennig's 1915 description, as 'holotypes'. This definition of a holotype is not valid, because Hennig's selection has priority. In 2011, [[Heinrich Mallison]] clarified that all the material known to Hennig in 1915, i.e. all the bones discovered before 1912, when [[Hermann Heck]] concluded the last German excavations, are [[Paralectotype|paralectotypesparalectotype]]s, and that MB.R.4800 is the correct lectotype.<ref>Mallison, H. (2011). The real lectotype of Kentrosaurus aethiopicus HENNIG, 1915. ''Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen'', 197-206.</ref>

[[Image:Kentrosaurus NTaethiopicus.jpgpng|thumb|[[Life restoration]]]]

''Kentrosaurus'' was a small stegosaur. It had the typical [[dinosauriandinosaur]]ian body [[Body plan|bauplan]], characterised by a small head, a long neck, short forelimbs and long hindlimbs, and a long, horizontal and muscular tail. Typical [[Stegosauridae|stegosaurid]] traits included the elongation and flatness of the head, the powerful build of the forelimbs, erect and pillar-like hindlimbs and an array of plates and spikes running along both sides of the top mid-line of the animal.<ref name=":3" />

''Kentrosaurus aethiopicus'' was a relatively small stegosaur, reaching {{cvt|4|-|4.5|m|ft}} in length and {{cvt|700|-|1600|kg|lb}} in body mass.<ref name=Janensch1925/>{{#tag:ref|p. 223 in Paul (2010)<ref name=Paul2010/>|group="upper-alpha"}}<ref name=MallCAE/><ref>{{Cite journal |lastlast1=Benson |firstfirst1=Roger B. J. |last2=Campione |first2=Nicolás E. |last3=Carrano |first3=Matthew T. |last4=Mannion |first4=Philip D. |last5=Sullivan |first5=Corwin |last6=Upchurch |first6=Paul |last7=Evans |first7=David C. |date=2014-05-06 |title=Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage |url=https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001853 |journal=PLOS Biology |language=en |volume=12 |issue=5 |pages=e1001853 |doi=10.1371/journal.pbio.1001853 |issn=1545-7885 |pmc=4011683 |pmid=24802911 |doi-access=free }}</ref> Some specimens suggest that relatively larger individuals could have existed.<ref name=Hennig1915/><ref name=Hennig1925/> These specimens are comparable to some ''[[Stegosaurus]]'' specimens in terms of the olecranon process in development.<ref>{{cite journal|last1=Woodruff|first1=D.C.|last2=Trexler|first2=D.|last3=Maidment|first3=S.C.R.|year=2019|title=Two New Stegosaur Specimens from the Upper Jurassic Morrison Formation of Montana, USA|doi=10.4202/app.00585.2018|journal=Acta Palaeontologica Polonica|volume=64|issue=3|pages=461–480|s2cid=201310639 |doi-access=free}}</ref>

The long tail of ''Kentrosaurus'' results in a position of the [[center of mass]] that is unusually far back for a [[quadrupedalism|quadrupedal]] animal. It rests just in front of the hip, a position usually seen in [[bipedalism|bipedal]] dinosaurs. However, the [[femur|femora]] are straight in ''Kentrosaurus'', as opposed to typical bipeds, indicating a straight and vertical limb position. Thus, the hindlimbs, though powered by massive thigh muscles attached to a long [[Ilium (bone)|ilium]], did not support the animal alone, and the very robust forelimbs took up 10 to 15% of the bodyweight.<ref name=MallROM/> The center of mass was not heavily modified by the [[osteoderm]]s (bony structures in skin) in ''Kentrosaurus'' or ''Stegosaurus'', which allowed the animals to stay mobile despite their armament. The hindlimbs’ thigh muscles were very powerful, allowing ''Kentrosaurus'' to reach a tripod stance on its hindlegs and tail.<ref>{{Cite journal |last=Mallison |first=H. |date=2014-03-07 |title=Osteoderm distribution has low impact on the centre of mass of stegosaurs |url=https://fr.copernicus.org/articles/17/33/2014/ |journal=Fossil Record |language=English |volume=17 |issue=1 |pages=33–39 |doi=10.5194/fr-17-33-2014 |issn=2193-0066|doi-access=free |bibcode=2014FossR..17...33M }}</ref>

Eight specimens from the skull, mandible, and teeth have been collected anand described from the Tendaguru Formation, most of them being isolated elements.<ref name=":2">Galton, P. M. (1988). [https://www.researchgate.net/profile/Peter-Galton/publication/272152710_Skull_bones_and_endocranial_casts_of_stegosaurian_dinosaur_Kentrosaurus_Hennig_1915_from_Upper_Jurassic_of_Tanzania_East_Africa/links/554197010cf2b790436be3bf/Skull-bones-and-endocranial-casts-of-stegosaurian-dinosaur-Kentrosaurus-Hennig-1915-from-Upper-Jurassic-of-Tanzania-East-Africa.pdf Skull bones and endocranial casts of stegosaurian dinosaur Kentrosaurus Hennig, 1915 from Upper Jurassic of Tanzania, East Africa.] ''Geologica et Palaeontologica'', ''22'', 123-143.</ref> Two [[Quadrate bone|quadrates]] (bones from the jaw joint) were referred to ''Kentrosaurus'', but they instead belong to a juvenile [[Brachiosauridae|brachiosaurid]].<ref>Maidment, S. C., Norman, D. B., Barrett, P. M., & Upchurch, P. (2008). Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia). ''Journal of Systematic Palaeontology'', ''6''(4), 367-407.</ref>

The long and narrow [[skull]] was small in proportion to the body. It had a small [[antorbital fenestra]], the hole between the nose and eye common to most [[Archosaur|archosaursarchosaur]]s, including modern birds, though lost in extant crocodylians. The skull's low position suggests that ''Kentrosaurus'' may have been a browser of low-growing vegetation. This interpretation is supported by the absence of premaxillary teeth and their likely replacement by a horny beak or [[Beak#Anatomy|rhamphotheca]]. The presence of a beak extended along much of the jaws may have precluded the presence of cheeks in stegosaurs.<ref name="czerkas1999">{{cite journal |last1=Czerkas |first1=S |year=1999 |title=The beaked jaws of stegosaurs and their implications for other ornithischians |journal=Miscellaneous Publication of the Utah Geological Survey |volume=99–1 |pages=143–150}}</ref> Due to its phylogenetic position, it is unlikely that ''Kentrosaurus'' had an extensive beak like ''Stegosaurus'' and it instead probably had a beak restricted to the jaw tips.<ref name="knoll2008">{{cite journal |last1=Knoll |first1=F |year=2008 |title=Buccal soft anatomy in ''Lesothosaurus'' (Dinosauria: Ornithischia) |url=https://www.researchgate.net/publication/233720216 |format=PDF |journal=Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen |volume=248 |issue=3 |pages=355–364 |doi=10.1127/0077-7749/2008/0248-0355}}</ref><ref name="barrett2001">Barrett, P.M. (2001). Tooth wear and possible jaw action of ''Scelidosaurus harrisonii'' Owen and a review of feeding mechanisms in other thyreophoran dinosaurs. Pp. 25-52 in Carpenter, K. (ed.): ''The Armored Dinosaurs''. Bloomington: Indiana University Press.</ref> Other researchers have interpreted these ridges as modified versions of similar structures in other ornithischians which might have supported fleshy cheeks, rather than beaks.<ref name="dinosauria04">{{cite book |title=The Dinosauria |vauthors=Galton PM, Upchurch P |publisher=University of California Press |year=2004 |isbn=978-0-520-24209-8 |veditors=Weishampel DB, Dodson P, Osmólska H |edition=2nd |chapter=Stegosauria}}</ref>

There are two nearly complete [[Neurocranium|braincases]] known from ''Kentrosaurus'' though they exhibit some taphonomic distortion.<ref name=":2" /> The [[Frontal bone|frontals]] and [[Parietal bone|parietals]] are flat and broad, with the latter bearing two transversely concave ventral sides with a ridge running down the middle that divides them. The lateral surface of the frontals form part of the [[Orbit (anatomy)|orbit]] (eye socket) and the medial side creates the anterior part of the [[Endocranium|endocranial cavity]] (braincase). [[Basilar part of occipital bone|Basioccipitals]] (where the skull articulated with the cervical vertebrae) form the posterior floor of the brain and the [[Occipital condyles|occipital condyle]], which is large and spherical in ''Kentrosaurus''. The rest of the braincase is formed by the [[Sphenoid bone|presphenoid]] composing the anterior end. The overall braincase morphology is very similar to those of ''[[Tuojiangosaurus]]'', ''[[Huayangosaurus]]'', and ''[[Stegosaurus]]''. However, the occipital condyle is a closer distance to the [[Sphenoid bone|basisphenoid tubera]] (bone at the front of the braincase) in ''Kentrosaurus'' and ''Huayangosaurus'' than in ''Tuojiangosaurus'' and some specimens of ''Stegosaurus''. Due to dinosaurs having more molding in their braincases, [[Endocast|endocastsendocast]]s of ''Kentrosaurus'' can be reconstructed using the preserved fossils. The brain is relatively short, deep, and small, with a strong [[Cerebral cortex|cerebral]] and [[pontine flexures]] and a steeply inclined posterodorsal edge when compared to those of other ornithischians. There is a small dorsal projection in the endocast where an unossified (lacking bone) region between the top of the [[supraoccipital]] (bone at the top-back of the braincase) and overlying parietal that was likely covered in [[cartilage]]. This characteristic is seen in other ornithischians. Because of the prominent flexures, many of the aspects of the brain can only be interpreted by the present structures.<ref name=":2" />

In the [[mandible]] (lower jaw), only an incomplete right dentary is known from ''Kentrosaurus''.<ref>Hennig, E. (1936). Ein dentale von Kentrurosaurus aethiopicus Hennig. ''Palaeontographica-Supplementbände'', 309-312.</ref> The deep dentary is almost identical in shape to that of ''Stegosaurus'', albeit much smaller. Similarly, the tooth is a typical stegosaurian tooth, small with a widened base and vertical grooves creating five ridges. The dentary has 13 preserved [[Dental alveolus|alvelovialveoli]] on the dorsomedial side and it they are slightly convex in lateral and dorsal views. On the surface adjacent to the alveoli, there is a shallow groove bearing small [[Vertebra|foramina]] (small openings in bone) that is similar to grooves on the dentary of the [[Cretaceous]] neornithischian ''[[Hypsilophodon]]'', with one foramina per tooth position. Stegosaurian teeth were small, triangular, and flat; wear facets show that they did grind their food.<ref name="FasWeis04">{{cite book |title=The Evolution and Extinction of the Dinosaurs |vauthors=Fastovsky DE, Weishampel DB |publisher=Cambridge University Press |year=2005 |isbn=978-0-521-81172-9 |veditors=Fastovsky DE, Weishampel DB |edition=2nd |pages=107–30 |chapter=Stegosauria: Hot Plates}}</ref> A single complete cheek tooth is preserved, with a large crown and long root. The crown notably has fewer marginal [[Denticle (tooth feature)|denticles]] and a prominent [[Cingulum (tooth)|cingulum]] compared to ''Stegosaurus'', ''Tuojiangosaurus'', and ''Huayangosaurus''.<ref name=":2" />

The neck was composed of 13 [[Cervical vertebrae|cervical]] (neck) vertebrae, the first being the [[Atlas (anatomy)|atlas]] which was strongly fused to the occipital region of the skull and followed by the [[Axis (anatomy)|axis]]. The other 11 cervicals had hourglass-shaped [[Vertebra|centra]] (the base of a vertebra) and rounded ventral [[Keel (anatomy)|keels]]. The [[diapophyses]] are large and strongly angled posteriorily and parallel to each other. The spinous processes got larger towards the posterior end, while the [[Articular processes|postzygapophyses]] became smaller and less horizontal, giving the anterior part of the neck lots of mobility laterally. The dorsal column consists of 13 [[Thoracic vertebrae|dorsal]] (back) vertebrae which are tall and have short centra. TheThey have a [[neural arch]] more than twice as high as the centrum, the vertebral body, and almost completely occupied by the extremely spacious [[neural canal]], a trait unique to ''Kentrosaurus.'' The diapophyses too were laterally elongated, creating a Y-shape in anterior view. The [[sacrum]] (part of pelvis with vertebrae) consists of 6 fused centra, the first being a loose sacrodorsal, while the rest of the centra’scentra's [[transverse processes]] (extensions of bone) are fused to the dorsal parts of the [[Rib cage|sacral ribs]] into a solid sacral plate. The ribs also fuse to the [[Ilium (bone)|ilium]] (the upper part of the pelvis) creating a fully ankylosed and solid sacrum. The ilium is notable in that the preacetabular process, front blade, of the [[Ilium (bone)|ilium]] widens laterally, to the front outer side, and does not taper unlike in all other stegosaurs. Another characteristic is that the length of the ilium equals, or is greater than, that of the thigh bone.<ref name="MallisonRealLecto" /> The [[Vertebra|caudal]] (tail) vertebrae are 29 in number, though 27-29 are coossified for attachment to the thagomizers (tail spikes). The caudal vertebrae are very unique, as they have a combination of transverse processes up to the 28th vertebra and rod-shaped processes on the posterior caudals. These posterior caudal processes have narrow bases that do not tough the plate formed by the fusion of the processes of the sacral vertebrae. ''Kentrosaurus'' can be distinguished from other members of the [[Stegosauria]] by a number of processes of the vertebrae, which in the tail do not run sub-parallel, as in most dinosaurs. In the front third of the tail, they point backwards, the usual direction. In the middle tail, however, they are almost vertical, and further back they are hook-shaped and point obliquely forward. The [[Chevron (anatomy)|chevrons]], bones pointing to below from the bottom side of the tail vertebrae, have the shape of an inverted T.<ref name="MallisonRealLecto" />

The [[scapula]] (shoulder blade) is sub-rectangular, with a robust blade. Though it is not always perfectly preserved, the [[acromion]] ridge is slightly smaller than in ''Stegosaurus''. The blade is relatively straight, although it curves towards the back. There is a small bump on the back of the blade, that would have served as the base of the [[triceps]] muscle. The [[coracoid]] is sub-circular.<ref>{{Cite journal |lastlast1=Maidment |firstfirst1=Susannah Catherine Rose |last2=Brassey |first2=Charlotte |last3=Barrett |first3=Paul Michael |date=2015-10-14 |title=The Postcranial Skeleton of an Exceptionally Complete Individual of the Plated Dinosaur Stegosaurus stenops (Dinosauria: Thyreophora) from the Upper Jurassic Morrison Formation of Wyoming, U.S.A. |url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0138352 |journal=PLOS ONE |language=en |volume=10 |issue=10 |pages=e0138352 |doi=10.1371/journal.pone.0138352 |issn=1932-6203 |pmc=PMC46056874605687 |pmid=26466098|bibcode=2015PLoSO..1038352M |doi-access=free }}</ref> The fore limbs were much shorter than the stocky hind limbs, which resulted in an unusual posture. The [[humerus]] (upper arm bone), like other stegosaurs, has greatly expanded proximal and distal ends that were attachment points between the coracoid and [[ulna]]-[[Radius (bone)|radius]] (forearm bones) respectively. The radius was larger than the ulna and had a wedge-shaped proximal end. The manus (hand) was small and had five toes with 2 toes bearing only a single phalange. The hindlimbs were much larger and too are similar to those of other stegosaurs. The [[femur]] (thigh bone) is the longest element in the body, with the largest known femur measuring 665 &nbsp;mm from the proximal to distal end. The [[tibia]] (shin bone) was wide and robust, while the fibula was skinny and thin without a greatly expanded distal end. The [[Pes (anatomy)|pes]] (foot) terminated in 3 toes, all of which had hoof-like [[Ungual|ungualsungual]]s (claws).<ref name=":3">Hennig, E. (1925). Kentrurosaurus aethiopicus; die Stegosaurierfunde vom Tendaguru, Deutsch-Ostafrika. ''Palaeontographica-Supplementbände'', 101-254.</ref><ref>Galton, P. M. (1982). The postcranial anatomy of stegosaurian dinosaur Kentrosaurus from the Upper Jurassic of Tanzania, East Africa.</ref><ref name=":2" />

Like the spikes and shields of [[Ankylosaur|ankylosaursankylosaur]]s, the [[Bonybony plate|bony plates]]s and spines of stegosaurians evolved from the low-keeled osteoderms characteristic of basal thyreophorans.<ref name="Norman">Norman, David (2001). "''Scelidosaurus'', the earliest complete dinosaur" in ''The Armored Dinosaurs'', pp 3-24. Bloomington: Indiana University Press. {{ISBN|0-253-33964-2}}.</ref> [[Peter Galton|Galton]] (2019) interpreted plates of an armored dinosaur from the [[Lower Jurassic]] ([[Sinemurian]]-[[Pliensbachian]]) Lower [[Kota Formation]] of [[India]] as fossils of a member of [[Ankylosauria]]; the author argued that this finding indicates a probable early Early Jurassic origin for both Ankylosauria and its [[sister group]] Stegosauria.<ref>{{Cite journal |author=Peter M. Galton |year=2019 |title=Earliest record of an ankylosaurian dinosaur (Ornithischia: Thyreophora): Dermal armor from Lower Kota Formation (Lower Jurassic) of India |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |volume=291 |issue=2 |pages=205–219 |doi=10.1127/njgpa/2019/0800 |s2cid=134302379}}</ref>

The vast majority of stegosaurian dinosaurs thus far recovered belong to the [[Stegosauridae]], which lived in the later part of the Jurassic and early Cretaceous, and which were defined by [[Paul Sereno]] as all stegosaurians more closely related to ''Stegosaurus'' than to ''Huayangosaurus''.<ref>Sereno, P.C., 1998, "A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria", ''Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen'' '''210''': 41-83</ref> This group is widespread, with members across the Northern Hemisphere, [[Africa]] and possibly [[South America]].<ref name=":0">{{Cite journal |lastlast1=Rauhut |firstfirst1=Oliver W. M. |last2=Carballido |first2=José Luis |last3=Pol |first3=Diego |date=2020-12-10 |title=First osteological record of a stegosaur (Dinosauria, Ornithischia) from the Upper Jurassic of South America |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1862133 |journal=Journal of Vertebrate Paleontology |language=en |volume=40 |issue=6 |pages=e1862133 |doi=10.1080/02724634.2020.1862133 |bibcode=2020JVPal..40E2133R |s2cid=234161169 |issn=0272-4634}}</ref> The South American remains come from [[Chubut Province|Chubut]], [[Argentina]] and consist only of a partial humerus, but the anatomy of the humerus is very similar to that of ''Kentrosaurus'' and both date to the Late Jurassic. In a phylogenetic analysis, the Chubut stegosaurid was recovered in polytomy with ''Kentrosaurus'' as basal stegosaurids, further suggesting that they are closely related.<ref name=":0" />

In Hennig’sHennig's 1915 description, ''Kentrosaurus'' was assigned to the family [[Stegosauridae]] due to the preservation of dermal armor and features like posterodorsally angled neural spines on the caudal vertebrae.<ref name="Hennig1915" /> This is confirmed by modern [[cladistic]] analyses, although in 1915 Stegosauridae was a far more inclusive concept that included some taxa now classified as ankylosaurs. A consecutive narrowing down of this concept caused ''Kentrosaurus'', until the 1980s to be seen as a typical "primitive" stegosaurian,<ref name="Norman1985" /> to be placed in a more derived, higher, position in the stegosaur evolutionary tree. However, recent analyses have consistently found ''Kentrosaurus'' to be in Stegosauridae, though typically as one of the most basal genera in the family.<ref>{{Cite journal |lastlast1=Hui |firstfirst1=Dai |last2=Ning |first2=Li |last3=Maidment |first3=Susannah C. R. |last4=Guangbiao |first4=Wei |last5=Yuxuan |first5=Zhou |last6=Xufeng |first6=Hu |last7=Qingyu |first7=Ma |last8=Xunqian |first8=Wang |last9=Haiqian |first9=Hu |last10=Guangzhao |first10=Peng |date=2022-03-30 |title=New stegosaurs from the Middle Jurassic Lower Member of the Shaximiao Formation of Chongqing, China |url=https://doi.org/10.1080/02724634.2021.1995737 |journal=Journal of Vertebrate Paleontology |volume=41 |issue=5 |pages=e1995737 |doi=10.1080/02724634.2021.1995737 |s2cid=247267743 |issn=0272-4634|doi-access=free }}</ref><ref name=":0" /><ref name=":1">{{Cite journal |lastlast1=Raven |firstfirst1=Thomas J. |last2=Maidment |first2=Susannah C. R. |date=2017 |title=A new phylogeny of Stegosauria (Dinosauria, Ornithischia) |url=https://onlinelibrary.wiley.com/doi/10.1111/pala.12291 |journal=Palaeontology |language=en |volume=60 |issue=3 |pages=401–408 |doi=10.1111/pala.12291|bibcode=2017Palgy..60..401R |hdl=10044/1/45349 |s2cid=55613546 |hdl-access=free }}</ref> ''Kentrosaurus'' has many traits not seen in other stegosaurids but seen in basal stegosaurians, such as the presence of a parascapular spine and maxillary teeth with only seven denticles at the margin.<ref name="Galton1982" /><ref name="Galton1990" /> Cladogram of Stegosauria below that includes nearly every known stegosaur genus, recovering ''Kentrosaurus'' as a basal stegosaurid:<ref name=":1" /><center>{{Clade|{{clade

The [[type species|type]] and sole accepted species of ''Kentrosaurus'' is ''Kentrosaurus aethiopicus'', named by Hennig in 1915. Fragmentary fossil material from Wyoming, named ''Stegosaurus longispinus'' by [[Charles W. Gilmore|Charles Gilmore]] in 1914,<ref name="Gilmore14" /> was in 1993 classified as a North American species of ''Kentrosaurus'', as ''K. longispinus''.<ref>{{cite journal | last1 = Olshevsky | first1 = G. | last2 = Ford | first2 = T.L. | year = 1993 | title = The Origin and Evolution of the Stegosaurs | journal = Kyoryugaku Saizensen | volume = 4 | pages = 64–103 }}</ref> However, this action was not accepted by the paleontological community, and ''S. longispinus'' has been assigned to its own genus, ''[[Alcovasaurus]]'', differing from ''Kentrosaurus'' in having more elongated tail spikes and the structure of the pelvis and vertebrae.<ref>Ulansky, R. E., 2014. Evolution of the stegosaurs (Dinosauria; Ornithischia). Dinologia, 35 pp. [in Russian]. [DOWNLOAD PDF] http://dinoweb.narod.ru/Ulansky_2014_Stegosaurs_evolution.pdf.</ref><ref>Ulansky, RE, 2014. Natronasaurus longispinus, 100 years with another name. Dinologia, 10 pp. [In Russian].</ref> Cladogram of the phylogenetic analysis of Stegosauridae conducted by Maidment ''et al'' (2019), which recovers a distinct ''Alcovasaurus'':<ref>{{Cite journal |lastlast1=Maidment |firstfirst1=Susannah C. R. |last2=Raven |first2=Thomas J. |last3=Ouarhache |first3=Driss |last4=Barrett |first4=Paul M. |date=2020-01-01 |title=North Africa's first stegosaur: Implications for Gondwanan thyreophoran dinosaur diversity |url=https://www.sciencedirect.com/science/article/pii/S1342937X19302217 |journal=Gondwana Research |language=en |volume=77 |pages=82–97 |doi=10.1016/j.gr.2019.07.007 |bibcode=2020GondR..77...82M |hdl=10141/622706 |s2cid=202188261 |issn=1342-937X|hdl-access=free }}</ref>

|2=''[[Miragaia longicollum|Miragaia]]'' }} }}

As the plates and spikes would have been obstacles during copulation, it is possible that pairs mated back-to-back with the female staying still in a [[Lordosis behavior|lordosis posture]] as the male maneuvers his penis into her [[cloaca]]. The shoulder spikes would have made the female unable to lie on her side during mating as is proposed for ''Stegosaurus''.<ref>{{cite journal|author=Isles, T.|year=2009|title=The socio-sexual behaviour of extant archosaurs: Implications for understanding dinosaur behaviour|journal=Historical Biology|volume=21|issue=3–4|pages=139–214|doi=10.1080/08912960903450505|bibcode=2009HBio...21..139I |s2cid=85417112|url=http://doc.rero.ch/record/232923/files/PAL_E4545.pdf}}</ref>

===DefenceDefense===

''Kentrosaurus'' would have coexisted with fellow ornithischians like ''[[Dysalotosaurus]] lettowvorbecki''; the [[sauropod]]s ''[[Giraffatitan]] brancai'', ''[[Dicraeosaurus]] hansemanni'' and ''D. sattleri'', ''[[Janenschia]] africana'', ''[[Tendaguria]]'' ''tanzaniensis'' and ''[[Tornieria|Tornieria africanus]]''; [[theropod]]s "[[Allosaurus]]" ''tendagurensis'', "Ceratosaurus" ''roechlingi'', "CeratosaurusTorvosaurus" ''ingens,'' ''[[Elaphrosaurus]] bambergi'', ''[[Veterupristisaurus]] milneri'' and ''[[Ostafrikasaurus]] crassiserratus''; and the [[pterosaur]] ''[[Tendaguripterus]] recki''.<ref name="WeishDinosauriaII" /><ref name="Barrettetal2008" /><ref name="Rauhut2011" /><ref name="Buffetaut2012" /> Other organisms that inhabited the Tendaguru included [[coral]]s, [[echinoderm]]s, [[cephalopod]]s, [[bivalve]]s, [[gastropod]]s, [[Decapoda|decapod]]s, sharks, [[Neopterygii|neopterygian]] fish, crocodilians and small mammals like ''[[Brancatherulum]] tendagurensis''.<ref name=Heinrich2001/>

<ref name=BardenMaidment2011>{{cite journal|authorsauthor1=Barden, H.E. & |author2=Maidment, S.C.R. |year=2011|title=Evidence for sexual dimorphism in the stegosaurian dinosaur ''Kentrosaurus aethiopicus'' from the Upper Jurassic of Tanzania|journal=Journal of Vertebrate Paleontology|volume=31|issue=3|pages=641–651|url=https://www.academia.edu/1477960|doi=10.1080/02724634.2011.557112|bibcode=2011JVPal..31..641B |s2cid=83521877}}</ref>

<ref name=Gilmore14>{{cite journal|last=Gilmore|first=C.W.|year=1914|title=Osteology of the armored Dinosauria in the United States National Museum, with special reference to the genus ''Stegosaurus''|journal=United States National Museum Bulletin|volume=81|pages=1–136|doi=10.5962/bhl.title.63658|url=https://www.biodiversitylibrary.org/bibliography/63658|doi-access=free}}</ref>

<ref name=Heinrich2001>{{cite journal|author=Heinrich, Wolf-Dieter|year=2001|title=The German‐TanzanianGerman-Tanzanian Tendaguru Expedition 2000|journal=Fossil Record|volume=4|issue=1|pages=223–237|doi=10.1002/mmng.20010040113|url=https://www.researchgate.net/publication/230461199|display-authors=etal|doi-access=free}}</ref>

<ref name=MallROM>{{cite journal|last=Mallison|first=H.|year=2010|title=CAD assessment of the posture and range of motion of ''Kentrosaurus aethiopicus'' HENNIG 1915|journal=[[Swiss Journal of Geosciences]]|volume=103|issue=2|pages=211–233|doi=10.1007/s00015-010-0024-2|s2cid=132746786|doi-access=free|bibcode=2010SwJG..103..211M }}</ref>

<ref name =Weishampel984>{{cite journal|author=Weishampel DB|year=1984|title=Interactions between Mesozoic Plants and Vertebrates: Fructifications and seed predation|journal=N. Jb. Geol. Paläontol. Abhandl.|pages=224–250|volume=167|issue=2 |doi=10.1127/njgpa/167/1984/224 }}</ref>

{{ThyreophoraStegosauria|S.}}